An important issue in large cryogenic power systems is that of maintenance, for example, the ability to easily access, maintain, and repair or interchange electric elements housed inside an evacuated Dewar. In order to achieve this, electronic elements must be removable. That is, one must be able to physically and electrically isolate an electrical element (including superconducting cables) and remove it from the system to maintain or repair the element without disrupting either the vacuum or the temperature control within the remainder of the system. This creates problems when superconducting busses are used to connect the various elements within the system. Superconducting cables currently in use and under development are not easily detachable. Disassembly can compromise the Dewar and vacuum spaces, increasing refrigeration loads (losses). FIG. 1 shows the current art 10, which is a completely sealed cryogenic container 28, 22, 28′ including welded sections, flanges or O-rings 11, 12. The cable 21 is continuous. In order to service the system, i.e., to assemble or replace a lead 21, the cryogenic spaces 23 need to be warmed, the cryogenic fluids or gases in the spaces 23 removed, and the vacuum system brought up to atmospheric pressure. Then, access to the leads 21 is accomplished by removing seals and, in some cases, un-welding some of the metallic vacuum spaces. Reassembly requires replacing the seals and in many cases re-welding the structure. This costs much time and labor.